Organic electroluminescent device

ABSTRACT

Disclosed is an organic electroluminescent device including a substrate, a first and second electrodes, and a light-emitting layer formed between the first electrode and the second electrode, and a hole-blocking layer formed between the light-emitting layer and the second electrode and using a material of a chemical formula 1.  
                 
 
     In this case, at least one of A 1  and A 2  is selected from a substituted or non-substituted aromatic group, a heterocyclic group, an aliphatic group, halogen, and hydrogen.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of Korean Application No.P2003-10393, filed on Feb. 19, 2003, which is hereby incorporated byreference as if fully set forth herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an organic luminescent device,and more particularly, to a hole-blocking layer.

[0004] 2. Discussion of the Related Art

[0005] Recently, with the trend of a large sized display, a request of aflat display that occupies a small area has been increased. One exampleof the flat display is an organic electroluminescent device also calledas an organic light emitting diode (OLED). And, technology for theorganic electroluminescent display is developed rapidly, whereby variousprototypes have been in market already.

[0006] The organic electroluminescent device emits light in a mannerthat electric charges are injected in an organic layer formed between ananode and a cathode so as to form a pair of electron and hole togenerate an exciton and an excited state of the exciton falls to aground state so as to emit light.

[0007] The organic electroluminescent device is not only formed on aflexible transparent substrate such as a plastic but also operated at alower voltage (less than 10V) compared to a plasma display panel or aninorganic electroluminescent display.

[0008] Also, the organic electroluminescent device has advantages inthat power consumption is reduced and various colors are available.

[0009] Moreover, the organic electroluminescent device enables toexpress three colors including green, blue, and red. Therefore, manyconcerns are focused on the organic electroluminescent device as thenext generation full color display.

[0010] The organic electroluminescent device generates an exciton bycoupling a hole from a hole transferring layer with an electron form thehole transferring layer, the exciton corresponding to a luminescentarea.

[0011] However, the exciton can be generated by the fast transferringspeed of the hole in another area except the luminescent area.

[0012] The exciton generated in another area except the luminescent areailluminates in that area only, thus, there is a problem lowering colorpurity and brightness.

[0013] Therefore, for increasing the performance and the brightness ofthe device, a material blocking a movement of the hole needs to beformed around the luminescent layer.

SUMMARY OF THE INVENTION

[0014] Accordingly, the present invention is directed to an organicelectroluminescent device that substantially obviates one or moreproblems due to limitations and disadvantages of the related art.

[0015] An object of the present invention is to provide an organicelectroluminescent device with enhanced brightness and color purity isobtained by forming a hole-blocking layer formed between thelight-emitting layer and a cathode.

[0016] Additional advantages, objects, and features of the inventionwill be set forth in part in the description which follows and in partwill become apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

[0017] To achieve these objects and other advantages and in accordancewith the purpose of the invention, as embodied and broadly describedherein, an organic electroluminescent device includes a substrate, afirst and second electrodes, and a light-emitting layer formed betweenthe first electrode and the second electrode, and a hole-blocking layerusing a material of a following chemical formula 1.

[0018] In this case, at least one of A₁ and A₂ is selected from asubstituted or non-substituted aromatic group, a heterocyclic group, analiphatic group, halogen, and hydrogen.

[0019] Structures of A₁ and A₂ the same or different. At least one of A₁and A₂ substituted or non-substituted is selected from phenyl, biphenyl,pyridyl, naphthyl, quinolyl, isoquinolyl, fluorenyl, terphenyl, methyl,ethyl, propyl, isopropyl, and halogen groups.

[0020] A substitute of the A₁ and A₂ is at least one selected from aryl,alkyl, aryloxy, alkoxy, arylamino, alkylamino, hydroxyl, amino, halogenand cyano group.

[0021] A substitute of the A₁ and A₂ is at least one selected fromphenyl, biphenyl, triphenyl, phenylethenyl, diphenylethenyl,phenylethynyl, phenoxy, tolyoxy, vinyl, methyl, ethyl, propyl,isopropyl, t-butyl, cyclohexyl, diphenylamino, carbazolyl, morpholinyl,methoxy, ethoxy, propoxy, butoxy, dimethylamino, diphenylamino, fluorineand chlorine group.

[0022] It is to be understood that both the foregoing generaldescription and the following detailed description of the presentinvention are exemplary and explanatory and are intended to providefurther explanation of the invention as claimed.

DETAILED DESCRIPTION OF THE INVENTION

[0023] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

[0024] In the present invention, a first electrode and a secondelectrode are formed on a in a vertical direction and a light-emittinglayer is formed between the first electrode and the second electrode.

[0025] A hole-blocking layer formed between the light-emitting layer andthe second electrode and using a material of a chemical formula 1.

[0026] In this case, at least one of A₁ and A₂ is selected from asubstituted or non-substituted aromatic group, a heterocyclic group, analiphatic group, a halogen, and hydrogen.

[0027] Structures of A₁ and A₂ can be the same or different. Also, atleast one of A₁ and A₂ is selected from a substituted or non-substitutedphenyl, biphenyl, pyridyl, naphthyl, quinolyl, isoquinolyl, fluorenyl,terphenyl, methyl, ethyl, propyl, isopropyl, and halogen groups.

[0028] Each substitute of the A₁ and A₂ is at least one selected fromaryl, alkyl, aryloxy, alkoxy, arylamino, alkylamino, hydroxyl, amino,halogen and cyano group.

[0029] Each substitute of the A₁ and A₂ is at least one selected fromphenyl, biphenyl, triphenyl, phenylethenyl, diphenylethenyl,phenylethynyl, phenoxy, tolyoxy, vinyl, methyl, ethyl, propyl,isopropyl, t-butyl, cyclohexyl, diphenylamino, carbazolyl, morpholinyl,methoxy, ethoxy, propoxy, butoxy, dimethylamino, diphenylamino, fluorineand chlorine group.

[0030] In this case, at least one of the A₁ and A₂ may be one of thefollowing chemical formulas 2.

[0031] The material of the hole-blocking layer may be at least one ofthe following chemical formulas.

[0032] According to the organic luminescent device of the presentinvention,(9-[4-(2,2-diphenyl-vinyl)-phenyl]-10-(4-trityl-phenyl)-anthracene),that is the B-60 used as the hole-blocking layer is compounded asfollows.

[0033] (1) Synthesis of tetraphenylmethyl boronic acid

[0034] First of all, 4-Bromotetra phenylmethane (1.62 g, 0.005 mol) isdissolved in THF (120 ml) in a dry 3-necks-r.b.f. 1.6 M of n-BuLi(3.9mL, 0.006 mol) melted in hexane is slowly added to the bath at −78° C.for ten minutes and the solution is stirred for 30 minutes at a roomtemperature.

[0035] And, after providing a bath at −78° C., trimethylborate(0.92 ml,00081 mol) is slowly added into the bath at −78 and stirred for 12 hoursat a room temperature.

[0036] Then, about 10% of HCl is slowly added into the bath at 0 formaking pH 2 or 3, and a resuted solution is extracted by usingdiethylether and distilled under a reduced pressure.

[0037] And, when a deposit is formed by petroleum ether, the solvent isfiltered whereby a white solid matter (1.25 g, 84%) of tetraphenylmethylboronic acid is obtained.

[0038] (2) Synthesis of 9-Bromo-10-(4-trityl-phenyl)-anthracene

[0039] First, tetraphenylmethyl boronic acid(1.19 g, 0.003 mol),9,10-DibromoAnthracene(2,74 g, 0.008 mol), tetrakis(triphenylphosphine)palladium(0)(0.19 g, 0.05 eq), Potassium carbonate(1.81 g, 0.013 mol)melted into Toluene(50 mL), THF(50 mL), and H₂O(50 mL) are admitted intoa two-neck-r.b.f. The solution is heated in a hot oil bath at about 100°C. and stirred for 24 hours. When the reaction is finished, THF andtoluene are removed.

[0040] And, after extracting a resulted solution by usingDichloromethane and water, the resulted solution is distilled underreduced pressure whereby silica gel column is obtained. The solution isre-crystallized by using Dichloromethane and methanol and filteredwhereby a yellow solid matter, namely,9-Bromo-10-(4-trityl-phenyl)-anthracene (0.98 g, 53%) is obtained.

[0041] (3) Synthesis of(9-[4-(2,2-Diphenyl-vinyl)-phenyl]-10-(4-trityl-phenyl)-anthracene)

[0042] 9-Bromo-10-(4-trityl-phenyl)-anthracene(0.35 g, 0.0006 mol),4-(2,2-Diphenyl-vinyl)-phenyl boronic acid(0.26 g, 0.0009 mol), tetrakis(triphenyl-phosphine)palladium(0)(0.035 g, 0.05 eq), Potassiumcarbonate(0.25 g, 0.002 mol) melted into Toluene(30 mL), THF(30 mL),H₂O(30 mL) are admitted into a two-neck-r.b.f. The solution is heated ina hot oil bath at about 100° C. and stirred for 24 hours. When thereaction is finished, THF and toluene are removed.

[0043] Silica gel column is obtained from the resulted solution by usinga ratio of Dichloromethane:Hexane=1:50.

[0044] The solvent is distilled under reduced pressure whereby a yellowsolid matter of 9-Bromo-10-(4-trityl-phenyl)-anthracene (0.98 g, 53%) isobtained.

[0045] The solvent is distilled under reduced pressure and filtered byusing methanol, whereby a yell solid matter of9-[4-(2,2-Diphenyl-vinyl)-phenyl]-10-(4-trityl-phenyl)-anthracene (0.42g, 91%) is obtained.

[0046] Hereinafter, a preferred embodiment of the organicelectroluminescent device will be described according to the presentinvention.

[0047] [Embodiment]

[0048] An ITO glass is patterned so as to have a size of 2 mm×2 mm. Thepatterned ITO glass is then cleaned.

[0049] A substrate is loaded on a vacuum chamber of which basic pressureis set up as 1×10⁻⁶ torr and CuPC(200Å), NPD(400Å),CBP+(btp)₂lr(acac)(8%) (200Å), the hole-blocking layer (100Å),Alq₃(300Å), LiF(5Å), Al(100Å) are deposited on the ITO in order.

[0050] When B-60 is used as the hole-blocking layer, 1135 cd/m²(9.30V)is shown at about 1 mA, brightness shows about 3.2 cd/A, whereby CIE isx=0.661, y=0.328.

[0051] [Comparative embodiment]

[0052] The ITO glass is patterned so as to have a size of 3 mm×3 mm. Thepatterned ITO glass is then cleaned. A substrate is loaded on a vacuumchamber of which basic pressure is set up as 1×10⁻⁶ torr and CuPC(200Å),NPD(400Å), CBP+(btp)₂lr(acac) (8%)(200Å), a light-emitting layer (100Å),Alq₃(300Å), LiF(5Å), Al(100Å) are deposited on the ITO in order.

[0053] When Balq is used as the hole-blocking layer, 1018cd/m²(9.97V)1135 cd/m²(9.30V) is shown at about 1 mA, brightness showsabout 1018 cd/m²(9.97V), whereby CIE x=0.659, y=0.329. Lifetime (half offirst brightness) shows 2000 cd/m² at about 1 mA.

[0054] Accordingly, the present invention is the organicelecroluminescent device including the hole-blocking layer between theanode and cathode. The organic elecroluminescent device with enhancedbrightness and color purity is obtained through the hole-blocking layer.

[0055] It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An organic electroluminescent device, comprising:a substrate; a first and second electrodes formed on the substrate; alight-emitting layer formed between the first electrode and the secondelectrode; and a hole-blocking layer formed between the light-emittinglayer and the second electrode and using a material of a chemicalformula
 1.

Wherein, at least one of A₁ and A₂ is selected from a substituted ornon-substituted aromatic group, a heterocyclic group, an aliphaticgroup, halogen, and hydrogen.
 2. The organic electroluminescent deviceof claim 1, wherein structures of A₁ and A₂ are the same or differenteach other.
 3. The organic electroluminescent device of claim 1, whereinat least one of A₁ and A₂ is selected from phenyl, biphenyl, pyridyl,naphthyl, quinolyl, isoquinolyl, fluorenyl, terphenyl, methyl, ethyl,propyl, isopropyl, and halogen groups.
 4. The organic electroluminescentdevice of claim 3, wherein a substitute of the A₁ and A₂ is at least oneselected from aryl, alkyl, aryloxy, alkoxy, arylamino, alkylamino,hydroxyl, amino, halogen and cyano group.
 5. The organicelectroluminescent device of claim 4, wherein a substitute of the A₁ andA₂ is at least one selected from phenyl, biphenyl, triphenyl,phenylethenyl, diphenylethenyl, phenylethynyl, phenoxy, tolyoxy, vinyl,methyl, ethyl, propyl, isopropyl, t-butyl, cyclohexyl, diphenylamino,carbazolyl, morpholinyl, methoxy, ethoxy, propoxy, butoxy,dimethylamino, diphenylamino, fluorine and chlorine group.
 6. Theorganic electroluminescent device of claim 1, wherein at least one ofthe A₁ and A₂ is one of the following chemical formulas
 2.


7. The organic electroluminescent device of claim 1, wherein a materialof the hole-blocking layer is one of the following chemical formulas 3.